High buoyancy composite materials

ABSTRACT

Ballistic resistant composite materials having high positive buoyancy in water are provided. More particularly, provided are foam-free, buoyant composite materials fabricated using dry processing techniques. The materials comprise fibrous plies that are partially coated with a particulate binder that is thermopressed to transform a portion of the binder into raised, discontinuous patches bonded to fiber/tape surfaces, while another portion of the particulate binder remains on the fibers/tapes as unmelted particles. The presence of the unmelted binder particles maintains empty spaces within the composite materials which increases the positive buoyancy of the composites in water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending U.S. application Ser. No.15/479,089, filed Apr. 4, 2017, which claims the benefit of U.S.Provisional Application Ser. No. 62/322,834 filed on Apr. 15, 2016, thedisclosures of which are incorporated by reference herein in theirentireties.

BACKGROUND Technical Field

The disclosure relates to ballistic resistant composite materials havingsuperior positive buoyancy in water. More particularly, the disclosurepertains to foam-free, buoyant composite materials fabricated using dryprocessing techniques.

Description of the Related Art

Soft body armor articles are typically fabricated in the form of textilegarments that contain compartments or pockets into which panels ofballistic resistant materials are positioned. For example, U.S. Pat. No.5,398,340 teaches a bullet resistant vest fabricated as a shell havingembedded anti-ballistic panels, wherein the shell is designed to keepthe panels in a proper protective position when the vest is worn by amoving officer. U.S. Pat. Nos. 7,636,948 and 9,222,757 each teach platecarrier designs including front and rear panel sections with uniquearrangements of pockets for supporting unique arrangements of ballisticplates and inserts. Most typically, such vests are designed so that theembedded plates are permanently sewn into the vest shell, rather thanthe plates simply being inserted into open pockets permitting them to beremoved.

Although this type of body armor is effective for protecting a user fromprojectile impact related injuries, it can have various disadvantages.First, the plates and other inserts are typically quite heavy andburdensome for the user to carry. Second, the plates are often quitelarge and restrictive of user mobility. Third, the plates typically haveeither neutral or negative buoyancy, which can affect the buoyancy ofthe complete armor article, and in many instances positive buoyancy isdesired.

Each of the first and second disadvantages identified above may beovercome by reducing the size of the armor plates, either by making theplates thinner and/or smaller. However, shrinking the size of the platessacrifices the degree of protective coverage and thereby limits theusefulness of the armor.

With regard to the issue of buoyancy, one conventionally known approachfor making soft body armor more buoyant is by adding buoyant insertsinto the vest design. See, for example, U.S. Pat. No. 6,892,392 whichteaches personal body armor having hard armor plates on the front andback regions of the vest and buoyant foam pads affixed to the interiorof the vest sections. U.S. Pat. No. 7,210,390 teaches a personalballistic protective device having a first layer comprised of ballisticmaterial and a second layer comprised of buoyant material such as aclosed-cell foam. U.S. Pat. No. 7,080,411 teaches an armor garmentincorporating an inflatable flotation bladder inside the garment.However, incorporating buoyant inserts adds substantial bulk to thearmor article, which reduces user comfort. Also, the above solutions areonly designed to address the problem of garment buoyancy and do notaddress the aforementioned weight and mobility concerns.

As an alternative strategy for overcoming the physical problemsassociated with heavy, bulky, non-buoyant armor, armor developers havedesigned solutions allowing vests to be quickly removed in emergencycircumstances, such as if a user falls into water. See, for example,U.S. Pat. Nos. 8,201,271 and 8,499,362 which teach armor vests havingquick release mechanisms allowing for the quick removal of the vest ifcircumstances demand its quick removal. U.S. Pat. No. 7,243,376 explainsthat soldiers have been known to drown due to the heavy weight of bodyarmor vests and teaches a cut away vest structure that may be quicklyand easily removed by a wearer. However, these solutions only havelimited usefulness and are not solutions for overcoming thedisadvantages of an armor system while in actual use.

Accordingly, there remains a need in the art for an optimized soft bodyarmor construction that is light, flexible and buoyant. The presentdisclosure provides a solution to this need.

SUMMARY

The disclosure provides soft body armor articles that are fabricatedfrom ballistic resistant materials having improved positive buoyancyrelative to the materials of the related art. The materials are formedusing dry processing techniques wherein extremely thin fibrous plies,formed from fibers and/or tapes (preferably multi-filament tapes), arepartially coated with a dry particulate binder, e.g. a powder binder,rather than a being coated with a liquid or molten binder. Theparticulate binder is only partially melted during processing, wherebythe fibers/tapes are only partially covered by discontinuous patches ofmelted and/or softened binder as well as unmelted polymer particles. Theresulting material has binder-free areas where portions of adjacentfibers/tapes are not touching each other and wherein empty spaces arepresent in said areas. The empty spaces thereby enhance the buoyancy ofthe material. When the material is used for the fabrication of softarmor plate carrier shells, it counterbalances the weight of anyincorporated plates having negative buoyancy and eliminates or minimizesthe need for bulky floatation components, such as foams. Additionally,the material provides enhanced anti-ballistic protection in areas whereplates are not incorporated, allowing the size of the plates to bereduced without risking loss of life.

As such, the disclosure provides a ballistic resistant materialcomprising at least one fibrous ply, each fibrous ply comprising aplurality of fibers and/or a plurality of tapes, wherein one or more ofsaid fibers/tapes have surfaces that are partially covered by raised,discontinuous patches of a polymeric binder bonded to and extending fromthe fiber/tape surfaces, and wherein the material further comprises aplurality of polymer particles on and/or between said fibers/tapes.

Also provided is a ballistic resistant material comprising:

a) a plurality of non-woven plies, each ply comprising a plurality ofadjacent, unidirectional fibers and/or a plurality of adjacent,unidirectional tapes, wherein one or more of said fibers/tapes havesurfaces that are partially covered by discontinuous patches of apolymeric binder bonded to the fiber/tape surfaces; each ply having anouter top surface and an outer bottom surface; and

b) at least one thermoplastic overlay bonded to at least one surface ofat least one of said plies, wherein said at least one thermoplasticoverlay only partially covers said at least one surface, and whereinsaid at least one thermoplastic overlay has a melting point below amelting point of said polymeric binder.

Further provided is a method for forming a ballistic resistant materialcomprising:

a) providing a first non-woven fibrous ply comprising an array ofadjacent, unidirectionally oriented fibers or an array of adjacent,unidirectionally oriented tapes, said first non-woven fibrous ply havingan outer top surface and an outer bottom surface

b) applying a dry, solvent-free particulate polymeric binder to at leastone surface of said first non-woven fibrous ply;

c) applying at least one thermoplastic overlay onto a surface of saidfirst non-woven fibrous ply, wherein said at least one thermoplasticoverlay only partially covers said surface, and wherein said at leastone thermoplastic overlay has a melting point below a melting point ofsaid polymeric binder; wherein steps b) and c) are reversible;

d) heating the at least one thermoplastic overlay to at least itssoftening temperature, and allowing it to bond to said surface of thefirst non-woven fibrous ply;

e) applying a second non-woven fibrous ply onto the first non-wovenfibrous ply on said at least one thermoplastic overlay, said secondnon-woven fibrous ply comprising an array of adjacent, unidirectionallyoriented fibers or an array of adjacent, unidirectionally orientedtapes, said second non-woven fibrous ply having first and secondsurfaces and said second non-woven fibrous ply comprising a dry,solvent-free particulate polymeric binder on at least one of saidsurfaces; and

f) consolidating said first non-woven fibrous ply and said secondnon-woven fibrous ply under heat and pressure wherein at least a portionof the particulate polymeric binder of the first non-woven fibrous plyand at least a portion of the particulate polymeric binder of the secondnon-woven fibrous ply are melted, and whereby said binders bond thefirst and second non-woven fibrous plies together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top-view scanned image of a 2-ply non-woven fabric coatedwith a powder resin.

FIG. 2 is a magnified top-view of a portion of FIG. 1, magnified at1.8×.

FIG. 3 is a top-view stereomicroscope image, magnified at 20×, of thefabric of FIG. 1.

FIG. 4 is a duplicate of the top-view stereomicroscope image of FIG. 3having the resin patches circled.

FIG. 5A is a top-view scanning electron microscope (SEM) photograph (atan order of magnitude of ×70) of a resin patch in the fabric of FIG. 1.

FIG. 5B is a top-view SEM photograph (at an order of magnitude of ×250)of the portion of the resin patch illustrated in FIG. 5A that isidentified by a white box.

FIG. 6A is a top-view SEM photograph (at an order of magnitude of ×70)of a resin patch in the fabric of FIG. 1.

FIG. 6B is a top-view SEM photograph (at an order of magnitude of ×250)of the portion of the resin patch illustrated in FIG. 6A that isidentified by a white box.

FIG. 7A is a top-view SEM photograph (at an order of magnitude of ×70)of a resin patch in the fabric of FIG. 1.

FIG. 7B is a top-view SEM photograph (at an order of magnitude of ×250)of the portion of the resin patch illustrated in FIG. 7A that isidentified by a white box.

FIG. 8A is a top-view SEM photograph (at an order of magnitude of ×70)of a resin patch in the fabric of FIG. 1.

FIG. 8B is a top-view SEM photograph (at an order of magnitude of ×250)of the portion of the resin patch illustrated in FIG. 8A that isidentified by a white box.

FIG. 9 is a top-view SEM photograph (at an order of magnitude of ×70) ofthree resin patches in the fabric of FIG. 1, also illustrating thepresence of binder particles.

FIG. 10 is a schematic representation of a flat-bed laminator.

FIG. 11 is a side-view schematic representation of a multilayerballistic resistant material having two fibrous plies coated with apowder binder and an intermediate scrim.

DETAILED DESCRIPTION

The composite materials provided herein are particularly intended forthe fabrication of ballistic resistant body armor, and therefore it isparticularly intended that the composite materials are to be fabricatedusing high tensile strength fibers and/or high tensile strength tapesthat are formed from high tensile strength fibers. However, the drybinder processing technique is equally applicable to the fabrication ofbuoyant non-armor articles, and therefore this disclosure should not beinterpreted as being limited to armor applications only nor to fibrouscomposites comprising high tenacity fibers only.

As used herein, a “fiber” is a long strand of a material, such as astrand of a polymeric material, the length dimension of which is muchgreater than the transverse dimensions of width and thickness. The fiberis preferably a long, continuous (but of a definite length) strand,rather than a short segment of a strand referred to in the art as a“staple” or “staple fiber.” A “strand” by its ordinary definition is asingle, thin length of something, such as a thread or fiber. Thecross-sections of fibers for use herein may vary widely, and they may becircular, flat or oblong in cross-section. They also may be of irregularor regular multi-lobal cross-section having one or more regular orirregular lobes projecting from the linear or longitudinal axis of thefilament. Thus the term “fiber” includes filaments, ribbons, strips andthe like having regular or irregular cross-section. It is preferred thatthe fibers have a substantially circular cross-section.

A single fiber may be formed from just one filament or from multiplefilaments. A fiber formed from just one filament is referred to hereinas either a “single-filament” fiber or a “monofilament” fiber, and afiber formed from a plurality of filaments is referred to herein as a“multifilament” fiber. Multifilament fibers as defined herein preferablyinclude from 2 to about 3000 filaments, more preferably from 2 to 1000filaments, still more preferably from 30 to 500 filaments, still morepreferably from 40 to 500 filaments, still more preferably from about 40filaments to about 240 filaments and most preferably from about 120 toabout 240 filaments. Multifilament fibers are also often referred to inthe art as fiber bundles or a bundle of filaments. As used herein, theterm “yarn” is defined as a single strand consisting of multiplefilaments and is used interchangeably with “multifilament fiber.” Theterm “tenacity” refers to the tensile stress expressed as force (grams)per unit linear density (denier) of an unstressed specimen. The term“initial tensile modulus” refers to the ratio of the change in tenacity,expressed in grams-force per denier (g/d) to the change in strain,expressed as a fraction of the original fiber/tape length (in/in).

The term “denier” is a unit of linear density equal to the mass in gramsper 9000 meters of fiber/yarn. In this regard, the fibers forming eachlayer may be of any suitable denier. For example, fibers may have adenier of from about 50 to about 5000 denier, more preferably from about200 to about 5000 denier, still more preferably from about 200 to about3000 denier, still more preferably from about 200 to about 1000 denier,and most preferably from about 200 to about 500 denier.

A “fibrous layer” as used herein may comprise any type of uni-axial ormulti-axial fabric, including a single-ply of unidirectionally orientedor randomly oriented (i.e. felted) non-woven fibers, a plurality ofplies of non-woven fibers/tapes that have been consolidated into asingle unitary structure, a single-ply of woven fabric, a plurality ofwoven fabric plies that have been consolidated into a single unitarystructure, a single-ply of knitted fabric or a plurality of knittedfabric plies that have been consolidated into a single unitarystructure. In this regard, a “layer” describes a generally planararrangement having an outer top (first) planar surface and an outerbottom (second) planar surface. The term “fibrous ply” as used hereinrefers to a single array of unidirectionally oriented fibers/tapes, asingle woven fabric, a single knitted fabric or a single felted fabric.Each fibrous ply will also have both an outer top surface and an outerbottom surface and a plurality of “fibrous plies” describes more thanone ply of the fibrous structures. A “single-ply” of unidirectionallyoriented fibers/tapes comprises an arrangement of fibers/tapes that arealigned in a unidirectional, substantially parallel array. This type ofarrangement is also known in the art as a “unitape”, “unidirectionaltape”, “UD” or “UDT.” As used herein, an “array” describes an orderlyarrangement of fibers, yarns or tapes, which is exclusive of woven andknitted fabrics, and a “parallel array” describes an orderly,side-by-side, coplanar parallel arrangement of fibers, yarns or tapes.The term “oriented” as used in the context of “oriented fibers/tapes”refers to the alignment direction of the fibers/tapes rather than tostretching of the fibers/tapes. The term “fabric” describes structuresthat may include one or more fibrous plies, with or withoutconsolidation/molding of the plies. A non-woven fabric formed fromunidirectional fibers/tapes typically comprises a plurality of non-wovenfibrous plies that are stacked on each other surface-to-surface in asubstantially coextensive fashion and consolidated. When used herein, a“single-layer” structure refers to any monolithic fibrous structurecomposed of one or more individual plies, wherein multiple plies havebeen merged by consolidation or molding techniques. The term “composite”in the context of this disclosure refers to combinations offibers/yarns/tapes with a polymeric binder material, and the term“fibrous” denotes materials made with fibers/yarns as well as tapes.

As used herein, a “high tensile strength” fiber is one which has atenacity of at least 10 g/denier, an initial tensile modulus of at leastabout 150 g/denier or more, and an energy-to-break of at least about 8J/g or more, each as measured by ASTM D2256. The high tensile strengthfibers preferably have a tenacity of greater than 10 g/denier, morepreferably at least about 15 g/denier, still more preferably at leastabout 20 g/denier, still more preferably at least about 27 g/denier,more preferably a tenacity of from about 28 g/denier to about 60g/denier, still more preferably from about 33 g/denier to about 60g/denier, still more preferably 39 g/denier or more, still morepreferably from at least 39 g/denier to about 60 g/denier, still morepreferably 40 g/denier or more, still more preferably 43 g/denier ormore, or at least 43.5 g/denier, still more preferably from about 45g/denier to about 60 g/denier, still more preferably at least 45g/denier, at least about 48 g/denier, at least about 50 g/denier, atleast about 55 g/denier or at least about 60 g/denier.

Particularly suitable high tenacity fibers include polyolefin fibers,such as high molecular weight polyethylene fibers, particularlyultra-high molecular weight polyethylene fibers, and polypropylenefibers. Also suitable are aramid fibers, particularly para-aramidfibers, polyamide fibers, polyethylene terephthalate fibers,polyethylene naphthalate fibers, extended chain polyvinyl alcoholfibers, extended chain polyacrylonitrile fibers, polybenzoxazole (PBO)fibers, polybenzothiazole (PBT) fibers, liquid crystal copolyesterfibers, rigid rod fibers such as M5® fibers, and glass fibers, includingelectric grade fiberglass (E-glass; low alkali borosilicate glass withgood electrical properties), structural grade fiberglass (S-glass; ahigh strength magnesia-alumina-silicate) and resistance grade fiberglass(R-glass; a high strength alumino silicate glass without magnesium oxideor calcium oxide). Each of these fiber types is conventionally known inthe art. Also suitable for producing polymeric fibers are copolymers,block polymers and blends of the above materials.

The most preferred fiber types for the second fibrous material andoptional third fibrous material are high performance fibers includingpolyethylene fibers (particularly extended chain polyethylene fibers),aramid fibers, PBO fibers, liquid crystal copolyester fibers,polypropylene fibers (particularly highly oriented extended chainpolypropylene fibers), polyvinyl alcohol fibers, polyacrylonitrilefibers, glass fibers and rigid rod fibers, particularly M5® rigid rodfibers. Specifically most preferred are polyethylene fibers and aramidfibers.

In the case of polyethylene, preferred fibers are extended chainpolyethylenes having molecular weights of at least 300,000, preferablyat least one million and more preferably between two million and fivemillion. Such extended chain polyethylene (ECPE) fibers may be grown insolution spinning processes such as described in U.S. Pat. No. 4,137,394or 4,356,138, which are incorporated herein by reference, or may be spunfrom a solution to form a gel structure, such as described in U.S. Pat.Nos. 4,413,110; 4,536,536; 4,551,296; 4,663,101; 5,006,390; 5,032,338;5,578,374; 5,736,244; 5,741,451; 5,958,582; 5,972,498; 6,448,359;6,746,975; 6,969,553; 7,078,099; 7,344,668 and U.S. patent applicationpublication 2007/0231572, all of which are incorporated herein byreference. Particularly preferred fiber types are any of thepolyethylene fibers sold under the trademark SPECTRA® from HoneywellInternational Inc. SPECTRA® fibers are well known in the art.

Particularly preferred methods for forming UHMW PE fibers are processesthat are capable of producing UHMW PE fibers having tenacities of atleast 39 g/denier, most preferably where the fibers are multi-filamentfibers. The most preferred processes include those described incommonly-owned U.S. Pat. Nos. 7,846,363; 8,361,366; 8,444,898;8,747,715; as well as U.S. publication no. 2011-0269359, the disclosuresof which are incorporated by reference herein to the extent consistentherewith. Such processes are called “gel spinning” processes, alsoreferred to as “solution spinning,” wherein a solution of ultra highmolecular weight polyethylene and a solvent is formed, followed byextruding the solution through a multi-orifice spinneret to formsolution filaments, cooling the solution filaments into gel filaments,and extracting the solvent to form dry filaments. These dry filamentsare grouped into bundles which are referred to in the art as eitherfibers or yarns. The fibers/yarns are then stretched (drawn) up to amaximum drawing capacity to increase their tenacity.

Preferred aramid (aromatic polyamide) fibers are well known andcommercially available, and are described, for example, in U.S. Pat. No.3,671,542. For example, useful aramid filaments are producedcommercially by DuPont under the trademark of KEVLAR®. Also usefulherein are poly(m-phenylene isophthalamide) fibers produced commerciallyby DuPont of Wilmington, Del. under the trademark NOMEX® and fibersproduced commercially by Teijin Aramid Gmbh of Germany under thetrademark TWARON®; aramid fibers produced commercially by KolonIndustries, Inc. of Korea under the trademark HERACRON®; p-aramid fibersSVM™ and RUSAR™ which are produced commercially by Kamensk Volokno JSCof Russia and ARMOS™ p-aramid fibers produced commercially by JSC ChimVolokno of Russia.

Suitable PBO fibers are commercially available and are disclosed forexample in U.S. Pat. Nos. 5,286,833, 5,296,185, 5,356,584, 5,534,205 and6,040,050, each of which is incorporated herein by reference. Suitableliquid crystal copolyester fibers are commercially available and aredisclosed, for example, in U.S. Pat. Nos. 3,975,487; 4,118,372 and4,161,470, each of which is incorporated herein by reference, andincluding VECTRAN® liquid crystal copolyester fibers commerciallyavailable from Kuraray Co., Ltd. of Tokyo, Japan. Suitable polypropylenefibers include highly oriented extended chain polypropylene (ECPP)fibers as described in U.S. Pat. No. 4,413,110, which is incorporatedherein by reference. Suitable polyvinyl alcohol (PV-OH) fibers aredescribed, for example, in U.S. Pat. Nos. 4,440,711 and 4,599,267 whichare incorporated herein by reference. Suitable polyacrylonitrile (PAN)fibers are disclosed, for example, in U.S. Pat. No. 4,535,027, which isincorporated herein by reference. Each of these fiber types isconventionally known and is widely commercially available. M5® fibersare formed from pyridobisimidazole-2,6-diyl(2,5-dihydroxy-p-phenylene)and were most recently manufactured by Magellan Systems International ofRichmond, Va. and are described, for example, in U.S. Pat. Nos.5,674,969, 5,939,553, 5,945,537, and 6,040,478, each of which isincorporated herein by reference. The term “rigid rod” fibers is notlimited to such pyridobisimidazole-based fiber types, and many PBO andaramid fiber varieties are often referred to as rigid rod fibers.Commercially available glass fibers include S2-Glass® S-glass fiberscommercially available from AGY of Aiken, S.C., HiPerTex™ E-Glassfibers, commercially available from 3B Fibreglass of Battice, Belgium,and VETROTEX® R-glass fibers from Saint-Gobain of Courbevoie, France.

As used herein, the term “tape” refers to a flat, narrow, monolithicstrip of material having a length greater than its width and an averagecross-sectional aspect ratio, i.e. the ratio of the greatest to thesmallest dimension of cross-sections averaged over the length of thetape article, of at least about 3:1. Known tapes may be fibrous ornon-fibrous, wherein a “fibrous” tape comprises one or more filaments.The cross-section of a tape of this disclosure may be rectangular, oval,polygonal, irregular, or of any shape satisfying the width, thicknessand aspect ratio requirements outlined herein.

Such tapes preferably have a substantially rectangular cross-sectionwith a thickness of about 0.5 mm or less, more preferably about 0.25 mmor less, still more preferably about 0.1 mm or less and still morepreferably about 0.05 mm or less. In the most preferred embodiments, thepolymeric tapes have a thickness of up to about 3 mils (76.2 μm), morepreferably from about 0.35 mil (8.89 μm) to about 3 mils (76.2 μm), andmost preferably from about 0.35 mil to about 1.5 mils (38.1 μm).Thickness is measured at the thickest region of the cross-section.

Tapes useful herein have preferred widths of from about 2.5 mm to about50 mm, more preferably from about 5 mm to about 25.4 mm, even morepreferably from about 5 mm to about 20 mm, and most preferably fromabout 5 mm to about 10 mm. These dimensions may vary but the tapes usedherein are most preferably fabricated to have dimensions that achieve anaverage cross-sectional aspect ratio, i.e. the ratio of the greatest tothe smallest dimension of cross-sections averaged over the length of thetape article, of greater than about 3:1, more preferably at least about5:1, still more preferably at least about 10:1, still more preferably atleast about 20:1, still more preferably at least about 50:1, still morepreferably at least about 100:1, still more preferably at least about250:1 and most preferred tapes have an average cross-sectional aspectratio of at least about 400:1.

Tapes are formed by conventionally known methods. For example, a fabricmay be cut or slit into tapes having a desired length. An example of aslitting apparatus is disclosed in U.S. Pat. No. 6,098,510 which teachesan apparatus for slitting a sheet material web as it is wound onto saidroll. Another example of a slitting apparatus is disclosed in U.S. Pat.No. 6,148,871, which teaches an apparatus for slitting a sheet of apolymeric film into a plurality of film strips with a plurality ofblades. The disclosures of both U.S. Pat. Nos. 6,098,510 and 6,148,871are incorporated herein by reference to the extent consistent herewith.Such methods are particularly useful for forming non-fibrous polymerictapes but the method of fabricating non-fibrous, polymeric tapes is notintended to be limiting.

Particularly useful methods for forming multi-filament fibrous tapes aredescribed in commonly-owned U.S. Pat. Nos. 8,236,119; 8,697,220;8,685,519; 8,852,714; 8,906,485, each of which is incorporated herein byreference to the extent consistent herewith. Each of these patentsdescribes methods where a multifilament feed fiber/yarn is compressedand flattened to form a tape. Particularly, U.S. Pat. No. 8,236,119teaches a process for the production of a polyethylene tape articlecomprising: (a) selecting at least one polyethylene multi-filament yarn,said yarn having a c-axis orientation function at least 0.96, anintrinsic viscosity when measured in decalin at 135° C. by ASTM D1601-99of from about 7 dl/g to about 40 dl/g, and said yarn having a tenacityof from about 15 g/d to about 100 g/d as measured by ASTM D2256-02 at a10 inch (25.4 cm) gauge length and at an extension rate of 100%/min; (b)placing said yarn under a longitudinal tensile force and subjecting saidyarn to at least one transverse compression step to flatten, consolidateand compress said yarn at a temperature of from about 25° C. to about137° C., thereby forming a tape article having an averagecross-sectional aspect ratio at least about 10:1, each said compressionstep having an outset and a conclusion wherein the magnitude of saidlongitudinal tensile force on each said yarn or tape article at theoutset of each said compression step is substantially equal to themagnitude of the longitudinal tensile force on the yarn or tape articleat the conclusion of that same compression step, and is at least about0.25 kilogram-force (2.45 Newtons); (c) stretching said tape article atleast once at a temperature in the range of from about 130° C. to about160° C. at a stretch rate of from about 0.001 min⁻¹ to about 1 min⁻¹;(d) optionally repeating step (b) one or more times at a temperaturefrom about 100° C. to about 160° C.; (e) optionally repeating step (c)one or more times; (f) optionally relaxing the longitudinal tensileforce between any of steps (b) to (e); (g) optionally increasing thelongitudinal tensile force between any of steps b) to (e); and (h)cooling said tape article to a temperature less than about 70° C. undertension. This process may also be modified by, prior to step (b),optionally continuously passing the yarn through one or more heatedzones at temperatures of from about 100° C. to about 160° C. undertension, followed by stretching the heated yarn at least once at astretch rate of from about 0.01 min⁻¹ to about 5 min⁻¹. The compressedand flattened multi-filament tapes formed according to the methods ofthese commonly-owned patents are particularly desirable herein.

Particularly suitable high-strength, high tensile modulus non-fibrouspolymeric tape materials are polyolefin tapes. Preferred polyolefintapes include polyethylene tapes, such as those commercially availableunder the trademark TENSYLON®, which is commercially available from E.I. du Pont de Nemours and Company of Wilmington, Del. See, for example,U.S. Pat. Nos. 5,091,133; 7,964,266; 7,964,267; and 7,976,930, all ofwhich are incorporated herein by reference. Also suitable arepolypropylene tapes, such as those commercially available under thetrademark TEGRIS® from Milliken & Company of Spartanburg, S.C. See, forexample, U.S. Pat. No. 7,300,691 which is incorporated herein byreference. Polyolefin tape-based composites that are useful as spallresistant substrates herein are also commercially available, for exampleunder the trademark DYNEEMA® BT10 from Royal DSM N.V. Corporation ofHeerlen, The Netherlands and under the trademark ENDUMAX® from TeijinAramid Gmbh of Germany. Also useful are the fibrous and non-fibroustapes described in commonly-owned U.S. Pat. Nos. 8,986,810; 9,138,961and 9,291,440, each of which is incorporated herein by reference to theextent consistent herewith. Non-fibrous, polymeric tapes useful hereinwill have the same preferred thicknesses and aspect ratios as thefiber-based tapes, but may be fabricated to have wider widths of fromabout 2.5 mm to about 21 cm, more preferably from about 2.5 mm to about10 cm, still more preferably from about 2.5 mm to 5 cm, still morepreferably from about 2.5 mm to about 25 mm, even more preferably fromabout 5 mm to about 20 mm, and most preferably from about 5 mm to about10 mm.

Like fibers, multi-filament tapes may be fabricated from the exact samepolymer types discussed above for fibers, because such tapes are formedby compressing and flattening such fibers. Accordingly, like fibers, thetapes may be of any suitable denier, preferably having a denier of fromabout 50 to about 30,000, more preferably from about 200 to about 10,000denier, still more preferably from about 650 to about 2000 denier, andmost preferably from about 800 to about 1500 denier. Additionally,useful tapes are preferably “high tensile strength” tapes having atenacity of at least 10 g/denier, an initial tensile modulus of at leastabout 150 g/denier or more, and an energy-to-break of at least about 8J/g or more, each as measured by ASTM D882-09 at 10 inch (25.4 cm) gaugelength and at an extension rate of 100%/min. The high tensile strengthtapes preferably have a tenacity of greater than 10 g/denier, morepreferably at least about 15 g/denier, still more preferably at leastabout 20 g/denier, still more preferably at least about 27 g/denier,more preferably a tenacity of from about 28 g/denier to about 60g/denier, still more preferably from about 33 g/denier to about 60g/denier, still more preferably 39 g/denier or more, still morepreferably from at least 39 g/denier to about 60 g/denier, still morepreferably 40 g/denier or more, still more preferably 43 g/denier ormore, or at least 43.5 g/denier, still more preferably from about 45g/denier to about 60 g/denier, still more preferably at least 45g/denier, at least about 48 g/denier, at least about 50 g/denier, atleast about 55 g/denier or at least about 60 g/denier, each as measuredby ASTM D882-09 at 10 inch (25.4 cm) gauge length and at an extensionrate of 100%/min.

The fibrous plies of this disclosure may individually comprise any typeof uni-axial or multi-axial fabric, including woven fabrics, non-wovenfabrics formed from unidirectionally oriented fibers/tapes, non-wovenfelted fabrics formed from randomly oriented fibers/tapes, or knittedfabrics. Woven fabrics may be formed using techniques that are wellknown in the art using any fabric weave, such as plain weave, crowfootweave, basket weave, satin weave, twill weave, three dimensional wovenfabrics, and any of their several variations. Plain weave is mostcommon, where fibers/tapes are woven together in an orthogonal 0°/90°orientation with warp fibers/tapes oriented perpendicular to weft (fill)fibers/tapes, and is preferred. The warp and weft (fill) count, known inthe art as a “pick count” or “mesh count,” is a measure of the densityof the woven fabric. Plain weave fabrics may have an equal or unequalwarp and weft count. In this regard, preferred first fibrous materialshave a preferred pick count of from about 20 ends per inch to about 80ends per inch in each of the warp and weft directions, more preferablyfrom about 25 ends per inch to about 70 ends per inch in each of thewarp and weft directions, and most preferably from about 25 ends perinch to about 60 ends per inch in each of the warp and weft directions.Preferred second fibrous materials have a preferred pick count of fromabout 15 ends per inch to about 70 ends per inch in each of the warp andweft directions, more preferably from about 20 ends per inch to about 60ends per inch in each of the warp and weft directions, still morepreferably from about 20 ends per inch to about 50 ends per inch in eachof the warp and weft directions, and most preferably from about 25 endsper inch to about 40 ends per inch in each of the warp and weftdirections.

Knit fabric structures are typically formed from fibers rather thantapes and are constructions composed of intermeshing loops, with thefour major types being tricot, raschel, net and oriented structures. Dueto the nature of the loop structure, knits of the first three categoriesare not as suitable as they do not take full advantage of the strengthof a fiber. Oriented knitted structures, however, use straight inlaidyarns held in place by fine denier knitted stitches. The fibers are verystraight without the crimp effect found in woven fabrics due to theinterlacing effect on the yarns. These laid in yarns can be oriented ina monoaxial, biaxial or multi-axial direction depending on theengineered requirements. It is preferred that the specific knitequipment used in laying in the load bearing yarns is such that theyarns are not pierced through.

Felts are also formed from fibers rather than tapes and may be formed byone of several techniques known in the art, such as by carding or fluidlaying, melt blowing and spin laying. A felt is a non-woven network ofrandomly oriented fibers, preferably at least one of which is adiscontinuous fiber, preferably a staple fiber having a length rangingfrom about 0.25 inch (0.64 cm) to about 10 inches (25.4 cm).

A non-woven unidirectional fibrous ply of the disclosure may be formedby conventional methods in the art, but without impregnating the plywith a resin, as discussed below. For example, in a preferred method offorming a non-woven unidirectional fibrous ply, a plurality offibers/tapes are arranged into an array, typically being arranged as aweb comprising a plurality of fibers/tapes aligned in a substantiallyparallel, unidirectional array. In a typical process that utilizesmulti-filament fibers, fiber bundles are supplied from a creel and ledthrough guides and one or more spreader bars into a collimating comb.This is typically followed by coating the fibers with a particulatepolymeric binder material. A typical fiber bundle (as well as a typicalmulti-filament tape) will have from about 30 to about 2000 individualfilaments. The spreader bars and collimating comb disperse and spreadout the bundled fibers, reorganizing them side-by-side in a coplanarfashion. Ideal fiber spreading results in the individual filaments orindividual fibers being positioned next to one another in a single fiberplane, forming a substantially unidirectional, parallel array of fiberswithout fibers overlapping each other. When tapes are utilized ratherthan fiber bundles, the tapes are arranged in a side-by-side array,preferably edge-to-edge without adjacent tapes overlapping each other,directly from a creel without the need to spread filaments usingspreader bars or a collimating comb.

Whether unidirectional non-woven, felted non-woven, woven or knitted,the ballistic effectiveness of the composite material is maximized bycombining and merging a plurality of fibrous plies into a unitarycomposite. In this regard, a plurality of single plies of the selectedfabric/fibrous ply type are stacked on top of each other in coextensivefashion and merged, i.e. consolidated, together. The number of plies inthe unitary composite will vary depending on the desired end use and thedesired ballistic resistance and weight requirements. In preferredembodiments, a multi-ply fibrous material preferably includes from 2 toabout 100 fibrous plies, more preferably from 2 to about 85 fibrousplies, and most preferably from about 2 to about 65 fibrous plies. Whenthe multi-ply composite comprises a plurality of unidirectionalnon-woven fibrous plies, it is typical for a plurality of such plies tofirst be formed into a 2-ply or 4-ply unidirectional non-woven fibrous“layer,” also referred to in the art as a “pre-preg,” prior to combininga plurality of such “layers” or “pre-pregs” together to form thesection. Each fibrous “layer” or “pre-preg” typically includes from 2 toabout 6 fibrous plies, typically being cross-plied at 0°/90°, but mayinclude as many as about 10 to about 20 fibrous plies as may be desiredfor various applications, with alternating layers preferably beingcross-plied at alternating 0°/90° orientations (although other angularorientations are also useful).

There are many means available for joining a plurality of fibrous pliestogether into a multi-ply structure, including mechanical means (e.g.,stitches, staples, rivets, bolts, screws, etc.) and adhesive means(i.e., with a polymeric binder, often referred to in the art as a“polymeric matrix”), with adhesive attachment being the most common.When combining non-woven plies in particular, a polymeric binder isgenerally also needed to initially to merge the fibers/tapes togetherinto individual ply form prior to forming pre-pregs and/or merging aplurality of plies together. Methods for applying a polymeric bindermaterial to fibrous plies/layers are well known in the art. In aconventional method of the prior art, a binder is applied as acontinuous coating, typically wherein fibers are fully coated orencapsulated by the binder, typically by coating fibers with a moltenpolymer or a polymer solution, thereby allowing the binder to flowaround and between fibers, especially when the fabrics arethermopressed. Additionally, in the conventional methods of the priorart, fibrous plies are formed by “impregnating” the plies with thebinder wherein the binder material diffuses into the fibrous ply and isnot simply on a surface of the ply, i.e., such that the fibers areembedded in or encapsulated by the binder polymer. However, in thepresent disclosure, the fibers/tapes are not coated with a moltenpolymer or a polymer solution, but rather with a particulate bindermaterial, and although the fibrous plies are attached to each otherusing adhesive means, the fibrous plies are not impregnated with,embedded in or encapsulated by the resin. Rather, they are surfacecoated only, and more specifically only partially surface coated, withdry polymer particles, some of which are softened and/or partiallymelted but which remain on the fiber/tape surfaces and remain localizedwithout flowing from their original location of application, and some ofwhich remain unsoftened and unmelted entirely. Particularly, dry polymerparticles, e.g., in the form of a powder, are applied to the fiber/tapesurfaces and, even after all desired processing steps are finished, aportion of the binder will remain in particulate form on and/or betweensome or all of the fibers/tapes.

Any useful method of applying the particulate binder may be employed,including particle/powder spraying, including conventional electrostaticspray methods such as corona powder spraying or tribo powder sprayingwith commercially available corona or tribo powder spraying equipment.Also useful is particle/powder sprinkling such as gravity sprinkling,which can be accomplished manually or can be automated, or any otherwell-known powder coating technique that will effectively coat thefibers/tapes with a dry particulate binder without using a liquidcarrier. Suitable powder spraying equipment is commercially available,for example, from Mitsuba Systems of Mumbai, India, such as theMultistatic Series 700, Sprayright Series 700, Tribo Series and IcoatSeries equipment from Mitsuba Systems, as well commercially availableAutomatic Powder Coating equipment from Mitsuba Systems. Also suitableare powder applicators commercially available from Nordson Corporationof Westlake, Ohio. One exemplary powder spraying apparatus useful hereinis described in U.S. Pat. No. 5,678,770 to Mitsuba Systems, which isincorporated herein by reference to the extent consistent herewith.Other useful methods are described in U.S. pre-grant publication2009/0169836, which is incorporated herein by reference to the extentconsistent herewith. Also useful are methods of electrostatic fluidized(dry) bed coating and electrostatic magnetic brush coating, which arewell known powder application techniques. The method of particleapplication is not intended to be strictly limiting except that theparticles are applied dry and solvent free, and this specificallyexcludes the application of particulate resins in the form solutions,emulsions or dispersions. This dry binder application method isparticularly desirable because it enables the resin to be applied to thefiber/tape surfaces without the need to support the fiber/tapes on arelease paper/film, which is conventionally needed when coatingunidirectional fiber arrays with a molten/liquid resin. In saidconventional methods, such a release paper must be removed prior tofurther processing, which adds additional, undesirable complexity to thefabrication process.

In order to optimize the anti-ballistic properties of the fibrousmaterials of the disclosure, it is preferred that the binder is suchthat the total weight of the binder in a fibrous material comprisesabout 30% by weight or less, more preferably about 20% by weight orless, still more preferably about 10% by weight or less, still morepreferably 7% by weight or less, still more preferably about 6% byweight or less and most preferably about 5% by weight or less of thefibrous material, based on the weight of the fibers/tapes plus theweight of the binder. In more preferred embodiments, the bindercomprises from about 2% to about 30% by weight, more preferably fromabout 2% to about 20%, still more preferably from about 2% to about 20%,still more preferably from about 2% to about 20%, and most preferablyfrom about 2% to about 10% by weight of the fibers/tapes plus the weightof the binder.

Suitable polymeric binder materials include both low tensile modulus,elastomeric materials and high tensile modulus materials. As used hereinthroughout, the term tensile modulus means the modulus of elasticity,which for polymeric binder materials is measured by ASTM D638. For thepurposes of this disclosure, a low modulus elastomeric material has atensile modulus measured at about 6,000 psi (41.4 MPa) or less accordingto ASTM D638 testing procedures. A low modulus polymer is preferably anelastomer having a tensile modulus of about 4,000 psi (27.6 MPa) orless, more preferably about 2400 psi (16.5 MPa) or less, still morepreferably 1200 psi (8.23 MPa) or less, and most preferably is about 500psi (3.45 MPa) or less. The glass transition temperature (Tg) of the lowmodulus elastomeric material is preferably less than about 0° C., morepreferably the less than about −40° C., and most preferably less thanabout −50° C. Preferred low modulus elastomeric materials also have apreferred elongation to break of at least about 50%, more preferably atleast about 100% and most preferably at least about 300%. Whether a lowmodulus material or a high modulus material, the polymeric binder mayalso include fillers such as carbon black or silica, may be extendedwith oils, or may be vulcanized by sulfur, peroxide, metal oxide orradiation cure systems as is well known in the art.

A wide variety of low modulus polymers and formulations may be utilizedas a binder sol long as that they are capable of being applied inparticulate form in accordance with this disclosure. Representativeexamples include polybutadiene, polyisoprene, natural rubber,ethylene-propylene copolymers, ethylene-propylene-diene terpolymers,polysulfide polymers, polyurethane elastomers, chlorosulfonatedpolyethylene, polychloroprene, plasticized polyvinylchloride, butadieneacrylonitrile elastomers, poly(isobutylene-co-isoprene), polyacrylates,polyesters, polyethers, fluoroelastomers, silicone elastomers,polyolefins (preferably thermoplastic polyolefins) includingpolyethylene and copolymers of ethylene, polyamides (useful with somefiber/tape types), acrylonitrile butadiene styrene, polycarbonates, andcombinations thereof, as well as other low modulus polymers andcopolymers curable below the melting point of the fiber. Also useful areblends of different elastomeric materials, or blends of elastomericmaterials with one or more thermoplastics.

Particularly useful are block copolymers of conjugated dienes and vinylaromatic monomers. Butadiene and isoprene are preferred conjugated dieneelastomers. Styrene, vinyl toluene and t-butyl styrene are preferredconjugated aromatic monomers. Block copolymers incorporatingpolyisoprene may be hydrogenated to produce thermoplastic elastomershaving saturated hydrocarbon elastomer segments. The polymers may besimple tri-block copolymers of the type A-B-A, multi-block copolymers ofthe type (AB). (n=2-10) or radial configuration copolymers of the typeR-(BA)_(x) (x=3-150);

wherein A is a block from a polyvinyl aromatic monomer and B is a blockfrom a conjugated diene elastomer. Many of these polymers are producedcommercially by Kraton Polymers of Houston, Tex. and described in thebulletin “Kraton Thermoplastic Rubber”, SC-68-81. Also useful are resindispersions of styrene-isoprene-styrene (SIS) block copolymer sold underthe trademark PRINLIN® and commercially available from HenkelTechnologies, based in Dusseldorf, Germany. Conventional low moduluspolymeric binder polymers employed in ballistic resistant compositesinclude polystyrene-polyisoprene-polystyrene block copolymers sold underthe trademark KRATON® commercially produced by Kraton Polymers.

Suitable particulate polyethylenes non-exclusively include VLDPE (VeryLow Density Polyethylene), LDPE (Low Density Polyethylene), LLDPE(Linear Low Density Polyethylene), MDPE (Medium Density Polyethylene),HDPE (High Density Polyethylene), poly(methylene), m-LDPE(metallocene-LDPE), m-LLDPE (metallocene-LLDPE), m-MDPE(metallocene-Medium Density Polyethylene) and COCs (Cyclic OlefinCopolymers). Such polyethylenes are commercially available, such as fromGoodfellow Corporation of Coraopolis, Pa. or Resinex of Buckinghamshire,United Kingdom. Useful ethylene copolymers non-exclusively includeethylene vinyl acetate (EVA), ethylene acrylic acid (EAA) and otherspreferably having high ethylene content.

Suitable particulate nylons non-exclusively include homopolymers orcopolymers selected from aliphatic polyamides and aliphatic/aromaticpolyamides having a molecular weight of from about 5,000 to about200,000. General procedures useful for the preparation of polyamides arewell known to the art. Such include the reaction products of diacidswith diamines. Useful diacids for making polyamides include dicarboxylicacids which are represented by the general formula

HOOC—Z—COOH

wherein Z is representative of a divalent aliphatic radical containingat least 2 carbon atoms, such as adipic acid, sebacic acid,octadecanedioic acid, pimelic acid, suberic acid, azelaic acid,dodecanedioic acid, and glutaric acid. The dicarboxylic acids may bealiphatic acids, or aromatic acids such as isophthalic acid andterephthalic acid. Suitable diamines for making polyamides include thosehaving the formula

H₂N(CH₂)_(n)NH₂

wherein n has an integer value of 1-16, and includes such compounds astrimethylenediamine, tetramethylenediamine, pentamethylenediamine,hexamethylenediamine, octamethylenediamine, decamethylenediamine,dodecamethylenediamine, hexadecamethylenediamine, aromatic diamines suchas p-phenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulphone, 4,4′-diaminodiphenylmethane, alkylated diamines such as2,2-dimethylpentamethylenediamine, 2,2,4-trimethylhexamethylenediamine,and 2,4,4 trimethylpentamethylenediamine, as well as cycloaliphaticdiamines, such as diaminodicyclohexylmethane, and other compounds. Otheruseful diamines include heptamethylenediamine, nonamethylenediamine, andthe like.

Useful polyamide homopolymers include poly(4-aminobutyric acid) (nylon4), poly(6-aminohexanoic acid) (nylon 6, also known aspoly(caprolactam)), poly(7-aminoheptanoic acid) (nylon 7),poly(8-aminooctanoic acid)(nylon 8), poly(9-aminononanoic acid) (nylon9), poly(10-aminodecanoic acid) (nylon 10), poly(11-aminoundecanoicacid) (nylon 11), poly(12-aminododecanoic acid) (nylon 12), while usefulcopolymers include nylon 4,6, poly(hexamethylene adipamide) (nylon 6,6),poly(hexamethylene sebacamide) (nylon 6,10), poly(heptamethylenepimelamide) (nylon 7,7), poly(octamethylene suberamide) (nylon 8,8),poly(hexamethylene azelamide) (nylon 6,9), poly(nonamethylene azelamide)(nylon 9,9), poly(decamethylene azelamide) (nylon 10,9),poly(tetramethylenediamine-co-oxalic acid) (nylon 4,2), the polyamide ofn-dodecanedioic acid and hexamethylenediamine (nylon 6,12), thepolyamide of dodecamethylenediamine and n-dodecanedioic acid (nylon12,12) and the like. Other useful aliphatic polyamide copolymers includecaprolactam/hexamethylene adipamide copolymer (nylon 6,6/6),hexamethylene adipamide/caprolactam copolymer (nylon 6/6,6),trimethylene adipamide/hexamethylene azelaiamide copolymer (nylontrimethyl 6,2/6,2), hexamethylene adipamide-hexamethylene-azelaiamidecaprolactam copolymer (nylon 6,6/6,9/6) and the like. Also included areother nylons which are not particularly delineated here.

Of these polyamides, preferred polyamides include nylon 6, nylon 6,6,nylon 6/6,6 as well as mixtures of the same. Of these, nylon 6 is mostpreferred.

Aliphatic polyamides used in the practice of this invention may beobtained from commercial sources or prepared in accordance with knownpreparatory techniques. For example, poly(caprolactam) can be obtainedfrom Honeywell International Inc., Morristown, N.J. under the trademarkCAPRON®.

Exemplary of aliphatic/aromatic polyamides includepoly(tetramethylenediamine-co-isophthalic acid) (nylon 4,1),polyhexamethylene isophthalamide (nylon 6,1), hexamethyleneadipamide/hexamethylene-isophthalamide (nylon 6,6/61), hexamethyleneadipamide/hexamethyleneterephthalamide (nylon 6,6/6T), poly(2,2,2-trimethyl hexamethylene terephthalamide), poly(m-xylyleneadipamide) (MXD6), poly(p-xylylene adipamide), poly(hexamethyleneterephthalamide), poly(dodecamethylene terephthalamide), polyamide6T/6I, polyamide 6/MXDT/I, polyamide MXDI, and the like. Blends of twoor more aliphatic/aromatic polyamides can also be used.

Aliphatic/aromatic polyamides can be prepared by known preparativetechniques or can be obtained from commercial sources. Other suitablepolyamides are described in U.S. Pat. Nos. 4,826,955 and 5,541,267,which are incorporated herein by reference.

High modulus, rigid materials generally have an initial tensile modulusgreater than 6,000 psi. Useful high modulus, rigid polymeric bindermaterials include polyurethanes (both ether and ester based), epoxies,polyacrylates, phenolic/polyvinyl butyral (PVB) polymers, vinyl esterpolymers, styrene-butadiene block copolymers, as well as mixtures ofpolymers such as vinyl ester and diallyl phthalate or phenolformaldehyde and polyvinyl butyral. However, low modulus bindermaterials are preferred over high modulus binder materials. Also usefulare the binder materials described in U.S. Pat. No. 6,642,159, thedisclosure of which is incorporated herein by reference. However, anyresin that is available or sold in the form of a solution, emulsion ordispersion must necessarily be separated from its solvent or liquidcarrier prior to deposition onto the fibers/tapes.

Most specifically preferred binder polymers are polar resins or polarpolymers, particularly polyurethanes within the range of both soft andrigid materials at a tensile modulus ranging from about 2,000 psi (13.79MPa) to about 8,000 psi (55.16 MPa). Such includes polyester-basedpolyurethanes and polyether-based polyurethanes, including aliphaticpolyester-based polyurethanes and aliphatic polyether-basedpolyurethanes. The most preferred polyurethanes are those having amodulus at 100% elongation of about 700 psi or more, with a particularlypreferred range of 700 psi to about 3000 psi. More preferred arealiphatic polyurethanes having a modulus at 100% elongation of about1000 psi or more, and still more preferably about 1100 psi or more. Mostpreferred is an aliphatic, polyether-based polyurethane having a modulusof 1000 psi or more, preferably 1100 psi or more.

In an embodiment where the binder comprises a blend of any of the abovematerials, it is preferred that the blend comprises two differentbinders having different melting points.

In this embodiment, the binder-coated fibrous plies may beheated/laminated at a temperature above the melting point of a firstbinder such that all of that first binder is softened and/or partiallymelted, but below the melting point of the second binder, such that noneof the second binder is softened or partially melted. For example, theparticulate binder blend may comprise a blend of a low modulus binderand a high modulus binder having differing melting points. Such mayinclude polymers that are chemically different (e.g., a blend of apolyester and an acrylic polymer) or chemically the same (e.g., a blendof a low modulus polyurethane and a high modulus polyurethane), as wouldbe determined by one skilled in the art.

In the process of the disclosure, prior to coating with the particulatebinder, the fibers/tapes are first pre-arranged into a continuous web ofthe desired fibrous structure (i.e., non-woven unidirectional, non-wovenfelt, woven or knitted) according to conventional fabrication methods.For example, in a typical method of forming a non-woven unidirectionalfibrous ply, a plurality of continuous fibers/tapes are formed into afiber/tape web comprising fibers/tapes aligned in a substantiallyparallel, unidirectional array of side-by-side fibers/tapes. Asdescribed above, when the fibrous ply is formed from multi-filamentfibers rather than tapes, this is typically accomplished by supplyingfiber bundles from a creel and leading the bundles through guides andone or more spreader bars into a collimating comb. The spreader bars andcollimating comb disperse and spread out the bundled fibers,reorganizing them side-by-side in a coplanar fashion.

Ideal fiber spreading results in the individual filaments or individualfibers being positioned next to one another in a single fiber plane,forming a substantially unidirectional, parallel array of fibers withoutfibers overlapping each other. When tapes are utilized rather than fiberbundles, the tapes are arranged in a side-by-side array, preferablyedge-to-edge without adjacent tapes overlapping each other, directlyfrom a creel without the need to spread filaments using spreader bars ora collimating comb.

After the tapes are arranged into a tape-based web (side-by-side arrayof tapes), or after the fibers are spread to form a fiber-based web (orafter one of the alternative fibrous web structures are formed byweaving, knitting or felting) the particulate binder is then applied tothe fibrous web according to the preferred application method.Thereafter, the coated web is then transferred to a flat-bed laminatorwhere the web is heated and pressed at a temperature above the meltingpoint of the binder polymer, followed by prompt cooling in a coolingsection of the flat-bed laminator. This continuous lamination stepeffectively softens and/or partially melts a portion of the polymerparticles, whereby those particles become sticky and bond to thefiber/tape surfaces, while another portion of the polymer particlesremain in unsoftened and/or unmelted dry particulate form and remainunbonded to the fiber/tape surfaces. The prompt cooling of the web alsoensures that there is no continued softening or partial melting of thebinder after this initial pressing.

In the preferred embodiments, the flat-bed laminator is a dual beltflat-bed laminator, such as the apparatus illustrated in FIG. 10. Thispreferred flat-bed laminator is described in greater detail incommonly-owned U.S. patent application Ser. No. 15/060,862, which isincorporated by reference herein to the extent consistent herewith. Asshown in FIG. 10, a binder coated fibrous web 20 is transported througha flat-bed laminator 30 which includes a first or upper belt 32 that isrotatable about a plurality of rollers 33, and a second or lower belt 34that is rotatable about a plurality of rollers 35. First and secondbelts 32, 34 may be coated with a non-stick coating, for example afluoropolymer-based material such as TEFLON®, commercially availablefrom E. I. du Pont de Nemours and Company of Wilmington, Del. First andsecond belts 32, 34 are spaced apart from each other by a passageway 36for fibrous web 20 to pass through. As shown in FIG. 10, illustrativefirst belt 32 rotates in a counter-clockwise direction and second belt34 rotates in a clockwise direction which advances fibrous web 20through flat-bed laminator 30. In one embodiment, first and second belts32, 34 rotate at a speed of 1-25 meters/second, and preferably 3meters/second to about 15 meters/second. Illustratively, first andsecond belts 32, 34 have approximately the same length such that fibrousweb 20 is in contact with both first and second belt 32, 34 forapproximately the same length of time.

Flat-bed laminator 30 of FIG. 10 further includes a heating portion orzone 38, a cooling portion or zone 40, and a plurality of nip orpressure rollers 42 positioned between heating portion 38 and coolingportion 40. As fibrous web 20 advances within flat-bed laminator 30,fibrous web 20 is heated in heating portion 38. For example, heatingportion 38 may be configured for operation at temperatures of as littleas 50° C., 60° C., 70° C., 80° C., or as great as 90° C., 100° C., 110°C., 120° C., 130° C., 140° C., 150° C., or any range delimited by anypair of the foregoing values. The temperature of heating portion 38 isto be set within the melting temperature range of the particulate bindersuch that a portion of the binder softens and/or partially melts inheating portion 38. In the most preferred embodiments, heating portion38 is set to and operates at a temperature of from about 100° C. toabout 140° C., and wherein the selected binders have melting pointswithin said range. In order to ensure that the particulate binder is notcompletely melted, the fibrous web 20 is heated for as little as about0.01 second, about 0.05 second, about 0.25 second, about 0.4 second,about 0.50 second, about 1.0 second, about 1.5 seconds, about 2.0seconds, about 2.5 seconds, about 3.0 seconds, about 4.0 seconds, about5.0 seconds, about 30 seconds, about 40 seconds, or as much as about 1minute, about 2 minutes, about 3 minutes, about 4 minutes, or about 5minutes, or any range delimited by any pair of the foregoing values, asdetermined by one skilled in the art depending on factors including themelting point of the selected binder and the temperature of the heatingportion 38.

As fibrous web 20 leaves heating portion 38, pressure is applied tofibrous web 20 through pressure rollers 42 while a portion of theparticles is partially softened and/or partially melted. Pressurerollers may be comprised of various materials, such as metals (e.g.,steel), polymers (e.g., elastic rubber), and/or ceramics. Additionally,one of pressure rollers 42 may have a fixed position and the other ofpressure rollers 42 may be movable when a force is applied thereto, suchthat when a force is applied to one of pressure rollers 42, a force alsois applied to fibrous web 20. More particularly, pressure rollers 42 mayapply a pressure of less than one bar to fibrous web 20. For example,pressure rollers 42 may apply a nip pressure to fibrous web 20 of 10psi, 30 psi, 50 psi, 70 psi, 90 psi, 110 psi, 130 psi, 150 psi, 170 psi,190 psi, 210 psi, 230 psi, 250 psi, 270 psi, 290 psi, 310 psi, or withinany range delimited by any pair of the foregoing values. In oneembodiment, pressure rollers may apply a pressure of 14 psi to fibrousweb 20. In the flat-bed laminator 30 as illustrated in FIG. 10, thegreatest pressure applied to fibrous web 20 occurs at a tangent 50 ofpressure rollers 42 which is parallel to first and second belts 32, 34.Different designs of flat-bed laminator 30 may apply different pressuresto fibrous web 20.

Pressure from pressure rollers 42 is applied to fibrous web 20 for about0.02 seconds to about 5 seconds. More particularly, pressure may beapplied to fibrous web 20 for a duration of time of as little as about0.01 second, about 0.045 second, about 0.4 second, about 0.50 second,about 1.0 second, about 1.5 seconds, about 2.0 seconds, about 2.5seconds, or as great as about 3.0 seconds, about 3.5 seconds, about 4.0seconds, about 4.5 seconds, about 5.0 seconds, or within any rangedelimited by any pair of the foregoing values. In one embodiment,pressure may be applied to fibrous web 20 for a time duration of fromabout 0.045 to about 0.4 second. Additionally, because pressure rollers42 have circular cross-sections, the aforementioned times signify thetotal time duration that fibrous web 20 experiences pressure.

After pressure is applied to fibrous web 20 with rollers 42, fibrous web20 moves through cooling portion 40 and then exits flat-bed laminator30. In one embodiment, cooling portion 40 is configured for temperaturesless than the melting temperature of the binder polymer. For example,cooling portion 40 may be configured for operation at temperatures of 0°C., 5° C., 10° C., 15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45°C., 50° C., 60° C., 70° C., 80° C., 90° C. or within any range delimitedby any pair of the foregoing values, depending on the particular binderpolymer. Because the length of cooling portion 40 is approximately thesame as the length of heating portion 38, fibrous web 20 may be cooledfor approximately the same amount of time it is heated. Moreparticularly, fibrous web 20 may be cooled for as little as about 0.01second, about 0.05 second, about 0.25 second, about 0.4 second, about0.50 second, about 1.0 second, about 1.5 seconds, about 2.0 seconds,about 2.5 seconds, about 3.0 seconds, about 4.0 seconds, about 5.0seconds, about 30 seconds, about 40 seconds, or as much as about 1minute, about 2 minutes, about 3 minutes, about 4 minutes, or about 5minutes, or any range delimited by any pair of the foregoing values. Inan alternative embodiment, cooling portion 40 may be eliminated fromflat-bed laminator 30 and the binder/composite will cool naturally to atemperature below the melting point of the binder.

As the fibrous web 20 passes through passageway 36, first and secondbelts 32, 34 may apply a low pressure to fibrous web 20 (i.e., apressure that is less than the pressure applied by rollers 42).Alternatively, belts 32, 34 may not apply any pressure to fibrous web 20when passing through chamber 36. In one example, first and second belts32, 34 may apply a pressure to fibrous web 20 of as little as about 0.01psi, about 0.05 psi, about 0.10 psi, about 0.15 psi, about 0.20 psi, orabout 0.25 psi, or as great as about 1.0 psi, about 2.0 psi, about 3.0psi, about 4.0 psi, about 5.0 psi, about 6.0 psi, about 7.0 psi, about8.0 psi, about 9.0, psi or about 10.0 psi, or within any range delimitedby any pair of the foregoing values, as fibrous web 20 passes throughheating portion 38 and cooling portion 40. In one embodiment, thepressure applied by first and second belts 32, 34 is less than about 0.5psi. More particularly, the pressure applied by first and second belts32, 34 is applied for a time duration which is inversely proportional tothe belt speed of flat-bed laminator 30. In one embodiment, theresidence time that pressure is applied to fibrous web 20 by first andsecond belts 32, 34 ranges from as little as about 1 second, about 3seconds, about 5 seconds, about 7 seconds, about 9 seconds, or about 11seconds, or as much as about 1 minute, about 2 minutes, about 3 minutes,about 4 minutes, or about 5 minutes, or any range delimited by any pairof the foregoing values. As such, fibrous web 20 may experience twodistinct pressures—a first low pressure applied by first and secondbelts 32, 34 when passing through heating and/or cooling portions 38,40, and a second higher pressure applied by pressure rollers 42.

While this particular flat-bed laminator 30 described above and theaforementioned lamination conditions are most preferred, the uniquematerials of this disclosure may be fabricated using other flat-bedlaminators or modified versions of flat-bed laminator 30, and the use ofthis specific flat-bed laminator illustrated in FIG. 10 is not intendedto be strictly limiting.

In the areas where the polymer particles are softened and/or partiallymelted, the pressure exerted on the fibrous web by pressure rollers 42(or an alternative press in an alternative apparatus) will partiallyflatten the particles into the above-referenced discontinuous patches.These patches are not fully flattened but rather remain as raised bumpsextending from the fiber/tape surfaces. Because the polymer forming thepatches is not heated enough to cause it to flow, the partiallyflattened patches will accordingly have a limited aspect ratio (i.e.,the ratio of the length to width of the patches). In preferredembodiments, the aspect ratio of the patches is preferably less than10:1, more preferably from about 1:1 to about 10:1, more preferably lessthan about 3:1, and most preferably from about 1:1 to about 3:1. Suchpatches are most clearly illustrated in FIGS. 5A, 5B, 6A, 6B, 7A, 7B,8A, 8B and 9, which are magnified SEM images showing close up views ofthe raised extending from the fiber/tape surfaces. Each of the imagedpatches in these magnified images was a portion of the fibrous compositeshown in FIGS. 1, 3 and 4. FIG. 2 is a magnified sectional view of thebottom right corner of the composite image of FIG. 1. FIG. 4 is aduplicate of FIG. 3 but with 9 localized patches marked for clarity.

As illustrated in FIGS. 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B and 9, thesepatches of binder bond portions of adjacent fibers (or adjacent tapes,not illustrated) to each other, enhancing the structural stability ofthe fibrous ply. Also of importance, in the areas where the binderremains in dry particulate form and unbonded to the fiber/tape surfaces,other portions of such adjacent fibers/tapes within the ply will remainunattached to each other. The presence of such unbonded, dry particlesis seen most clearly in FIGS. 2, 6A and 9. Unexpectedly, the presence ofsuch dry particles combined with the discontinuous patches has beenfound to enhance the buoyancy of the fibrous material by maintaining thefibrous plies as partially open structures wherein empty spaces aremaintained within the plies, as shown most clearly in FIGS. 3, 4, 5A and9. In the final product, the remaining particles preferably have anaverage particle size (diameter) of from about 50 μm to about 700 μm,more preferably from about 80 μm to about 600 μm, still more preferablyfrom about 80 μm to about 500 μm, still more preferably from about 80 μmto about 400 μm, still more preferably from about 80 μm to about 300 μm,still more preferably from about 80 μm to about 200 μm and mostpreferably from about 100 μm to about 200 μm. Preferably, at least about90% of the particles have a particle size (diameter) that is within 40μm of the average particle size.

As discussed above, after the particle coated fiber/tape web isprocessed through the flat-bed laminator, the web is then cut to adesired length to form a plurality of fibrous plies of the desiredlengths, and thereafter a desired number of plies are stacked on eachother surface-to-surface in a substantially coextensive fashion andconsolidated into a unitary composite. With particular regard to fibrousmaterials comprising a plurality of unidirectional non-woven fibrousplies, it is conventionally known in the art to coextensively stackindividual fibrous plies upon each other such that the unidirectionallyoriented fibers/tapes in each fibrous ply are oriented in a non-parallellongitudinal fiber/tape direction relative to the longitudinalfiber/tape direction of each adjacent ply. Most typically, the fibrousplies are cross-plied orthogonally at 0° and 90° angles wherein theangle of the fibers/tapes in even numbered layers is preferablysubstantially the same and the angle of the fibers/tapes in odd numberedlayers is preferably substantially the same, but adjacent plies can bealigned at virtually any angle between about 0° and about 90° withrespect to the longitudinal fiber/tape direction of another ply. Forexample, a five ply non-woven structure may have plies oriented at a0°/45°/90°/45°/0° or at other angles. Such rotated unidirectionalalignments are described, for example, in U.S. Pat. Nos. 4,457,985;4,748,064; 4,916,000; 4,403,012; 4,623,574; and 4,737,402, all of whichare incorporated herein by reference to the extent compatible herewith.With particular regard to fibrous materials comprising one or more wovenfibrous plies, it is also typical for the warp and weft componentfibers/tapes forming a single fibrous material to be orientedorthogonally to each other.

Merging of the multiple plies into unitary composite structures may beaccomplished using conventional techniques in the art, including bothlow pressure consolidation techniques and high pressure moldingtechniques, with or without heat. Methods of consolidating fibrousplies/layers are well known, such as by the methods described in U.S.Pat. No. 6,642,159. In the preferred embodiments, consolidation ispreferably conducted under mild conditions, i.e., at temperaturesranging from about 50° C. to about 175° C., more preferably from about95° C. to about 175° C. and most preferably from about 105° C. to about175° C., and at pressures ranging from about 5 psig (0.034 MPa) to about2500 psig (17 MPa), more preferably from about 5 psig to about 100 psig(0.69 MPa), with a duration of from about 0.01 seconds to about 24hours, more preferably from about 0.02 seconds to about 2 hours, stillmore preferably from about 5 seconds to about 2 hours and mostpreferably from about 30 seconds to about 1 hour. Consolidation may beconducted, for example, by passing the stack through a calender nip set,by pressing in a flat-bed laminator (such as that described above andillustrated in FIG. 10), a double belt or steel belt press or in anautoclave. Consolidation may also be conducted by vacuum molding thematerial in a mold that is placed under a vacuum. Vacuum moldingtechnology is well known in the art. Most commonly, consolidation isconducted using a flat-bed laminator.

Alternatively, the stack of plies may be merged together using highpressure merging in a suitable molding apparatus at a pressure of fromabout 50 psi (344.7 kPa) to about 5,000 psi (34,470 kPa), morepreferably about 100 psi (689.5 kPa) to about 3,000 psi (20,680 kPa),most preferably from about 150 psi (1,034 kPa) to about 1,500 psi(10,340 kPa). Molding may alternately be conducted at higher pressuresof from about 5,000 psi (34,470 kPa) to about 15,000 psi (103,410 kPa),more preferably from about 750 psi (5,171 kPa) to about 5,000 psi, andmore preferably from about 1,000 psi to about 5,000 psi. The moldingstep may take from about 4 seconds to about 45 minutes. However, inorder to ensure that the unsoftened and/or unmelted portion of theparticulate binder does not melt during a high pressure molding step,molding should be conducted at relatively low temperatures. In thisregard, preferred molding temperatures range from about 200° F. (˜93°C.) to about 350° F. (˜177° C.), more preferably at a temperature fromabout 200° F. to about 300° F. (˜149° C.) and most preferably at atemperature from about 200° F. to about 280° F. (˜138° C.).

While each of the molding and consolidation techniques described hereinare similar and the terms are often used interchangeably in the art,“molding” as used herein specifically refers to a method of merging bybonding fibrous plies/layers together in a batch process, while“consolidation” refers to a method of merging by bonding fibrousplies/layers together in a generally continuous process. However, thisis not intended to be strictly limiting. Also, in either process,suitable temperatures, pressures and times are generally dependent onthe type of polymeric binder coating materials, polymeric bindercontent, process used and fiber/tape type.

As discussed above, as a result of the dry coating process describedherein, the resulting materials have binder-free areas where portions offiber/tape surfaces are not coated with the binder, neither in patchform nor in particle form. In general, only one surface of each fibrouslayer will be coated with the particulate binder, and accordingly about50% or less of the fiber/tape surface area of each individual fibrousply will be coated with the particulate binder. It is noted that theprocess of passing the fibrous web through the flat-bed laminator andconsolidation of the multi-ply stack of fibrous plies, which causesflattening of a portion of the binder particles, will thereby slightlyincrease the surface area coverage. Nevertheless, even after theseprocessing steps, it is preferred that less than 50% of the surface areais covered by the binder, preferably less than about 40%, preferablyless than about 30%, preferably less than about 20%, more preferablyfrom about 2% to about 20%, still more preferably from about 5% to about15%, and most preferably from about 5% to about 10% of the surface areaof the fibers/tapes in each fibrous ply.

By virtue of utilizing a particulate powder rather than a liquid binderor molten binder, fibrous plies of this disclosure may be fabricatedhaving extremely low areal densities while maintaining effective levelsof ballistic resistance. In preferred embodiments, each fibrous ply ofthe disclosure has a preferred total areal density (i.e. the fiber arealdensity (FAD) plus the binder areal density) of about 125 g/m² or less,more preferably about 100 g/m² or less, still more preferably about 95g/m² or less, still more preferably about 90 g/m² or less, still morepreferably about 85 g/m² or less, still more preferably about 80 g/m² orless, still more preferably about 75 g/m² or less, and most preferablyabout 70 g/m² or less, with most preferred areal density ranges of fromabout 20 g/m² to about 80 g/m² or from about 30 g/m² to about 80 g/m².For the purposes of this disclosure, the FAD is the same for fiber-basedand multifilament tape-based plies/composites because the multifilamenttapes are simply flattened and compressed versions of the same fibers.

In embodiments where the total areal density per fibrous ply isextremely low, i.e. where the individual ply total areal density is lessthan 100 g/m², these low values are typically obtained where the fibrousplies are in the form of unidirectional non-woven fibrous plies thathave been subjected to extensive fiber spreading or extensiveflattening/compression during tape formation. In these embodiments, theFAD levels are also exceedingly low, i.e., about 80 g/m² or less, morepreferably about 70 g/m² or less, still more preferably about 60 g/m² orless, still more preferably about 50 g/m² or less and most preferablyabout 40 g/m² or less, with most preferred fiber areal density rangingfrom about 15 g/m² to about 80 g/m² or from about 30 g/m² to about 60g/m². Preferred binder coating weights range from about 1 g/m² to about20 g/m², more preferably from about 2 g/m² to about 15 g/m², and mostpreferably from about 3 g/m² to about 10 g/m². However, at suchexceedingly low FAD values, the fibrous plies can have low stability andvery difficult to handle, making them very difficult to process throughthe flat-bed laminator or difficult to consolidate. Accordingly, whenply stability is a concern, the stability may be improved by applyingone or more thin thermoplastic overlays onto a surface of the fibrousweb. The thermoplastic overlay may be, for example, a discontinuousthermoplastic web, an ordered discontinuous thermoplastic net, anon-woven discontinuous adhesive fabric, a non-woven discontinuousadhesive scrim, a porous film or a plurality of thin thermoplasticpolymer strips. Suitable polymers for the thermoplastic overlaynon-exclusively include thermoplastic polymers non-exclusively may beselected from the group consisting of polyolefins, polyamides,polyesters (particularly polyethylene terephthalate (PET) and PETcopolymers), polyurethanes, vinyl polymers, ethylene vinyl alcoholcopolymers, ethylene octane copolymers, acrylonitrile copolymers,acrylic polymers, vinyl polymers, polycarbonates, polystyrenes,fluoropolymers and the like, as well as co-polymers and mixturesthereof, including ethylene vinyl acetate (EVA) and ethylene acrylicacid. Also useful are natural and synthetic rubber polymers. Of these,polyolefin and polyamide layers are preferred. The preferred polyolefinis a polyethylene. Non-limiting examples of useful polyethylenes are lowdensity polyethylene (LDPE), linear low density polyethylene (LLDPE),Medium Density Polyethylene (MDPE), linear medium density polyethylene(LMDPE), linear very-low density polyethylene (VLDPE), linear ultra-lowdensity polyethylene (ULDPE), high density polyethylene (HDPE) andco-polymers and mixtures thereof. Of these, the most preferredpolyethylene is MDPE.

In a preferred embodiment, the thermoplastic overlay is aheat-activated, non-woven, adhesive web, such as SPUNFAB®, commerciallyavailable from Spunfab, Ltd, of Cuyahoga Falls, Ohio (trademarkregistered to Keuchel Associates, Inc.). Also suitable are THERMOPLAST™and HELIOPLAST™ webs, nets and films, commercially available fromProtechnic S.A. of Cernay, France. Of all the above, most preferred is apolyamide web, particularly SPUNFAB® polyamide webs. SPUNFAB® polyamidewebs have a melting point of typically from about 75° C. to about 200°C., but this is not limiting.

When the thermoplastic overlay is a scrim such as a SPUNFAB® web, theoverlay is preferably very thin, having a preferred layer thickness offrom about 1 μm to about 250 μm, more preferably from about 5 μm toabout 25 μm and most preferably from about 5 μm to about 9 μm. Whilesuch thicknesses are preferred, it is to be understood that otherthicknesses may be produced to satisfy a particular need and yet fallwithin the scope of the present disclosure. It should also be understoodthat these thicknesses are not necessarily descriptive of continuouswebs. For example, SPUNFAB® webs are several mils thick where materialis present, but most of the web is just air. These materials are betterdescribed by their basis weight, e.g. particularly preferred is aSPUNFAB® web having a basis weight of 6 g/m². The thermoplastic overlaypreferably comprises from about 1% to about 25% by weight of the overallcomposite, more preferably from about 1% to about 17% percent by weightof the overall composite and most preferably from 1% to 12%, based onthe weight of the fibers/tapes plus the binder plus the weight of theoverlay(s).

In another preferred embodiment, the thermoplastic overlay comprisesthin thermoplastic polymer strips in the form of binding elongatebodies. As used herein, a “binding” elongate body is an elongate bodysuch as a fiber that at least partially comprises a heat activatedthermoplastic polymer having a melting temperature below a meltingtemperature of the structural fibers/tapes (e.g., the high tenacityfibers/tapes), and preferably having a melting temperature that is thesame as or below that of the polymeric binder. Such binding elongatebodies are conventionally known in the art and non-exclusively includebodies such as fibers comprising ethylene-vinyl acetate,ethylene-acrylate copolymers, styrene block copolymers, polyurethanes,polyamides, polyesters and polyolefins, including and most preferablypolyethylene. In this embodiment, only a minimal amount of bindingbodies are needed to properly stabilize the fibrous web or fibrous ply,and in most applications it is sufficient to apply binding fibers acrossthe entire width of the fibrous web or ply at one or two inch intervalsdown the length of the web/ply.

The thermoplastic overlay(s) is (are) preferably bonded to at least onefibrous ply using well known techniques, such as thermal lamination.Typically, lamination is performed by positioning the fibrous ply andoverlay(s) on one another coextensively as discussed above and thecombination is pressed through the nip of a pair of heated laminatingrollers under conditions of sufficient heat and pressure and accordingto techniques well known in the art to cause the layers to combine intoa unitary film. Such lamination heating may be may performed at the sametemperatures, pressures, rate and other conditions as discussed abovefor processing the binder coated fibrous plies through flat-bedlaminator 30.

In one embodiment, the thermoplastic overlay(s) may be applied to asingle binder-coated fibrous ply followed by bonding the overlay(s) tothe single ply by passing the combination through a laminator. Inanother embodiment, the thermoplastic overlay(s) may serve as anintermediate adhesive layer between two binder-coated fibrous plieswherein a second binder-coated fibrous ply is applied on top of theoverlay(s) after the overlay(s) is (are) applied onto the first fibrousply, followed by passing the combination through the laminator. In oneparticularly preferred method, a first non-woven fibrous ply is providedthat has a dry, solvent-free particulate polymeric binder on at leastone surface; at least one thermoplastic overlay is then applied onto asurface of the first non-woven fibrous ply such that the overlay(s) onlypartially cover the surface ply; the thermoplastic overlay(s) is (are)then optionally heated to at least its softening temperature to allow itto bond to the surface of the first ply; a second non-woven fibrous plyhaving a dry, solvent-free particulate polymeric binder on at least onesurfaces is then applied onto the first non-woven fibrous ply on top ofthe overlay(s); and then the combination is consolidated under heat andpressure wherein at least a portion of the particulate polymeric binderof the first non-woven fibrous ply and at least a portion of theparticulate polymeric binder of the second non-woven fibrous ply aremelted, and whereby said binders bond the first and second non-wovenfibrous plies together.

A multilayer structure 100 formed by this method is schematicallyrepresented in FIG. 11, wherein a first unidirectional fibrous ply 140having fibers oriented at 0° is combined with a thermoplastic scrim 160and second unidirectional fibrous ply 180 having fibers oriented at 90°.Each of the unidirectional fibrous plies is coated on their outersurfaces with a particulate binder 120 such that the binder and overlayare positioned on opposite surfaces of each fibrous ply. Variations ofthis method may also be practiced as would be determined by one skilledin the art. For example, the overlay(s) may be applied onto a surface ofthe fibrous plies prior to applying the binder onto an opposite surface,or two fibrous plies may be joined together with each having aparticulate binder and one or more thermoplastic overlays on oppositesurfaces prior to adjoining them. In another embodiment, both theparticulate binder and the one or more thermoplastic overlays may beapplied onto each outer surface of each fibrous ply.

In addition to or alternative to the option of incorporating thethermoplastic overlay(s) between fibrous plies in a multi-ply composite,it may be desired to attach a polymeric film to one or both of the outersurfaces of a multi-ply material. Such is well known in the art ofballistic resistant composites. In these embodiments, particularlypreferred polymer films non-exclusively include thermoplastic polymerlayers including polyolefins, polyamides, polyesters (particularlypolyethylene terephthalate (PET) and PET copolymers), polyurethanes,vinyl polymers, ethylene vinyl alcohol copolymers, ethylene octanecopolymers, acrylonitrile copolymers, acrylic polymers, vinyl polymers,polycarbonates, polystyrenes, fluoropolymers and the like, as well asco-polymers and mixtures thereof, including ethylene vinyl acetate (EVA)and ethylene acrylic acid. Of these, polyolefin and polyamide layers arepreferred. The preferred polyolefin is a polyethylene. Non-limitingexamples of useful polyethylenes are low density polyethylene (LDPE),linear low density polyethylene (LLDPE), medium density polyethylene(MDPE), linear medium density polyethylene (LMDPE), linear very-lowdensity polyethylene (VLDPE), linear ultra-low density polyethylene(ULDPE), high density polyethylene (HDPE) and co-polymers and mixturesthereof. Such thermoplastic polymer layers are preferably very thin,having preferred layer thicknesses of from about 1 μm to about 250 μm,more preferably from about 5 μm to about 25 μm and most preferably fromabout 5 μm to about 9 μm. While such thicknesses are preferred, it is tobe understood that other thicknesses may be produced to satisfy aparticular need and yet fall within the scope of the present disclosure.Such thermoplastic polymer layers may be bonded to the outer compositesurfaces using well known techniques, such as by thermal lamination in aflat-bed laminator under the conditions discussed above, before, duringor after merging together the individual fibrous plies into a unitary,consolidated composite. Additionally, or alternatively, one or moresurfaces of a fibrous ply or of the unitary, consolidated composite maybe coated with protective coating, such as a coating providing waterrepellent properties. Suitable coatings non-exclusively include naturalrubber, polyvinyl chloride, polyurethane, silicone elastomers,fluoropolymers, and waxes, as would be determined by one skilled in theart. Particularly preferred water resistant polymer coatingsnon-exclusively include fluoropolymer based coatings, such asOLEOPHOBOL™ water repellent agents commercially available from HuntsmanLLC of Salt Lake City, Utah, and polyurethane coatings.

The multi-ply composite materials fabricated herein according to theabove methods achieve a unique composite structure that retains asubstantial volume of empty space within the interior of the compositearticle. In a typical embodiment, a composite material formed accordingto the above methods will comprise an empty space volume that is greaterthan 20% of the total volume of the composite material, preferably fromabout 20% to about 30% of the total volume of the composite material andarticles formed therefrom, and thereby yielding materials havingsubstantially enhanced positive buoyancy in water relative tocomparative materials having lower empty space volumes. Importantly,these materials allow the formation of ballistic resistant articleshaving superior positive buoyancy, such as buoyant plates for use inballistic resistant vests, without requiring the use of other buoyancyenhancing components, such as foams or air bladders, and therebyfulfilling a longstanding need in the art. These benefits are alsoextended to many other non-ballistic related industries as well wherebuoyant fabrics may be desired, including applications such as air bags(e.g. for hovercrafts), sail cloths and other marine fabrics, as well asother applications where light weight is more important than buoyancy,such as air curtains, textile reinforcements for architecturalstructures, awnings, banners, flags, canopies, tents, parachutes, tarps,backpacks, footwear, etc. The following non-limiting examples serve toillustrate the invention:

Example 1

A continuous, non-woven web of parallel SPECTRA® fibers (1300 denierSPECTRA® 1000 fibers) is prepared having a width of 38 cm. A dry, lowdensity polyethylene (LDPE) powder was manually sprinkled onto onesurface of the web, partially coating the surface such that 20% of thesurface area of the one surface is coated with the powder. A pluralityof squares are cut from this web having length×width dimensions of 38cm×38 cm. Two squares (plies) are formed into a stack with the pliesarranged in 0°/90° cross-plied orientations relative to the longitudinalaxes of their component fibers, and the resin comprises about 10% byweight of the combined 2-ply material. The two-ply material is thenpassed through a flat-bed laminator wherein they are pressed togetherfor 30 seconds at 100° C. and under contact pressure of about 50 psiwhereby they are attached to each other. The LDPE powder is onlypartially melted, forming some raised, discontinuous patches of the LDPEbonded to and extending from the fiber surfaces and also leavingplurality of polymer particles on and between the fibers. The resultingmaterial has 22% empty space volume and exhibits excellent positivebuoyancy.

Example 2

Example 1 is repeated but prior to mating the two plies together one orboth of the plies is/are stabilized with a thermoplastic overlay bondedto at least one of their surfaces. The thermoplastic overlay is aplurality of binding polymer strips applied laterally across the plyorthogonal to the longitudinal fiber axis. The binding polymer stripsare formed from a heat activated polyethylene having a melting pointbelow the melting point of the LDPE powder.

Example 3

Example 2 is repeated except the thermoplastic overlay is aheat-activated, non-woven, adhesive SPUNFAB® web, commercially availablefrom Spunfab, Ltd. (SPUNFAB® 408HWG 6-gsm fusible polyolefin resin web).The SPUNFAB® is added to the top side of the bottom ply (its position asit is passed through the flat-bed laminator).

Example 4

Example 1 is repeated except the web is formed from high tenacity UHMWPEfibrous tapes having a tenacity of approximately 33 g/denier that weremade according to a process described in U.S. Pat. No. 8,236,119. Thetapes averaged about 3/16 inch wide and had an aspect ratio of greaterthan 10:1 and the web is arranged with tape edges contacting each otherbut without adjacent tapes overlapping each other.

While the present disclosure has been particularly shown and describedwith reference to preferred embodiments, it will be readily appreciatedby those of ordinary skill in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe disclosure. It is intended that the claims be interpreted to coverthe disclosed embodiment, those alternatives which have been discussedabove and all equivalents thereto.

1. A ballistic resistant material comprising at least one fibrous ply,each fibrous ply comprising a plurality of fibers and/or a plurality oftapes, wherein one or more of said fibers/tapes have surfaces that arepartially covered by raised, discontinuous patches of a polymeric binderbonded to and extending from the fiber/tape surfaces, and wherein thematerial further comprises a plurality of polymer particles on and/orbetween said fibers/tapes, wherein said patches of the polymeric binderand said polymer particles comprise different polymers and wherein atleast some of said polymer particles are unsoftened.
 2. The ballisticresistant material of claim 1 wherein the patches have an aspect ratioof less than 10:1 and are formed on the fiber/tape surfaces by softeningand/or partially melting a dry, solvent-free polymeric powder, whereinsaid patches are flattened powder particles in the form of raised bumpsthat extend from the fiber/tape surfaces, and wherein the polymerforming the patches has not been heated enough to flow from its originallocation of application.
 3. The ballistic resistant material of claim 1wherein said unsoftened polymer particles are unmelted.
 4. The ballisticresistant material of claim 1 wherein each fibrous ply comprises aplurality of adjacent, unidirectional fibers and/or a plurality ofadjacent, unidirectional tapes, and wherein said particles are both onand between said fibers/tapes.
 5. The method of claim 19 wherein saidpolymeric binder and said polymer particles comprise the same polymer.6. The ballistic resistant material of claim 1 wherein less than 50% ofthe surface area of each of said fibers/tapes is covered by saidpatches.
 7. The ballistic resistant material of claim 1 wherein eachfibrous ply is non-woven and comprises a plurality of adjacent,unidirectional, parallel fibers/tapes, and wherein from 2% to 20% of thesurface area of each of said fibers/tapes is covered by said polymericbinder.
 8. The ballistic resistant material of claim 1 wherein eachfibrous ply has a fiber areal density of less than 80 g/m² and a totalareal density of less than 100 g/m².
 9. The ballistic resistant materialof claim 6 wherein the patches of polymeric binder and the plurality ofpolymer particles combined comprise about 6 wt. % or less by weight ofthe ballistic resistant material, and wherein said particles have anaverage particle size of from about 100 μm to about 200 μm.
 10. Amultilayer composite comprising a plurality of consolidated plies of theballistic resistant material of claim 1, wherein said plies have beenconsolidated under heat and pressure.
 11. The multilayer composite ofclaim 10 wherein said composite has an interior empty space volume of atleast 20% of the volume of said composite.
 12. A ballistic resistantmaterial comprising: a) a plurality of non-woven plies, each plycomprising a plurality of adjacent, unidirectional fibers and/or aplurality of adjacent, unidirectional tapes, wherein one or more of saidfibers/tapes have surfaces that are partially covered by discontinuouspatches of a polymeric binder bonded to the fiber/tape surfaces; eachply having an outer top surface and an outer bottom surface; and b) atleast one thermoplastic overlay bonded to at least one surface of atleast one of said plies, wherein said at least one thermoplastic overlayonly partially covers said at least one surface, and wherein said atleast one thermoplastic overlay has a melting point below a meltingpoint of said polymeric binder, and wherein the material furthercomprises a plurality of polymer particles on and between saidfibers/tapes, wherein said patches of the polymeric binder and saidpolymer particles comprise different polymers.
 13. The ballisticresistant material of claim 12 wherein the thermoplastic overlaycomprises a non-woven, discontinuous adhesive web, wherein at least someof said polymer particles are unsoftened and not bonded to the fibersurfaces and wherein said particles have an average particle size offrom about 50 μm to about 700 μm.
 14. The ballistic resistant materialof claim 12 wherein the thermoplastic overlay comprises one or morebinding elongate bodies having a melting point below a melting point ofsaid polymeric binder.
 15. The ballistic resistant material of claim 12wherein the non-woven plies are consolidated and wherein said ballisticresistant material has a volume that partially comprises empty space,wherein said empty space comprises greater than 20% of said ballisticresistant material.
 16. The ballistic resistant material of claim 15wherein said material has a fiber areal density of less than about 80g/m².
 17. The ballistic resistant material of claim 12 wherein thethermoplastic overlay comprises a non-woven, discontinuous adhesive web;wherein at least some of said polymer particles are unsoftened and notbonded to the fiber surfaces; wherein the patches have an aspect ratioof less than 10:1 and are formed on the fiber/tape surfaces by softeningand/or melting a dry, solvent-free polymeric powder, and wherein saidunsoftened polymer particles are unmelted and have an average particlesize of from about 80 μm to about 500 μm.
 18. The ballistic resistantmaterial of claim 12 wherein at least some of said polymer particles areunsoftened, wherein said unsoftened polymer particles are unmelted andare not bonded to the fiber surfaces, wherein said particles are both onand between said fibers/tapes, and wherein said patches are flattenedpowder particles in the form of raised bumps that extend from thefiber/tape surfaces.
 19. A method for forming a ballistic resistantmaterial comprising: a) providing a first non-woven fibrous plycomprising an array of adjacent, unidirectionally oriented fibers or anarray of adjacent, unidirectionally oriented tapes, said first non-wovenfibrous ply having an outer top surface and an outer bottom surface b)applying a dry, solvent-free particulate polymeric binder to at leastone surface of said first non-woven fibrous ply; c) applying at leastone thermoplastic overlay onto a surface of said first non-woven fibrousply, wherein said at least one thermoplastic overlay only partiallycovers said surface, and wherein said at least one thermoplastic overlayhas a melting point below a melting point of said polymeric binder;wherein steps b) and c) are reversible; d) heating the at least onethermoplastic overlay to at least its softening temperature, andallowing it to bond to said surface of the first non-woven fibrous ply;e) applying a second non-woven fibrous ply onto the first non-wovenfibrous ply on said at least one thermoplastic overlay, said secondnon-woven fibrous ply comprising an array of adjacent, unidirectionallyoriented fibers or an array of adjacent, unidirectionally orientedtapes, said second non-woven fibrous ply having first and secondsurfaces and said second non-woven fibrous ply comprising a dry,solvent-free particulate polymeric binder on at least one of saidsurfaces; and f) consolidating said first non-woven fibrous ply and saidsecond non-woven fibrous ply under heat and pressure wherein at least aportion of the particulate polymeric binder of the first non-wovenfibrous ply and at least a portion of the particulate polymeric binderof the second non-woven fibrous ply are melted, and whereby said bindersbond the first and second non-woven fibrous plies together.
 20. Themethod of claim 19 wherein the at least one thermoplastic overlay andthe particulate polymeric binder of said first non-woven fibrous ply areapplied to opposite surfaces of said first non-woven fibrous ply.